1. Field of the Invention
This invention relates to integrated circuit packaging and, more particularly, to semiconductor memory encased within a molded resin to form a memory module having edge connectors aligned substantially within a row near the edge of the module. The edge connectors are configured as substantially planar pads extending along an outer surface of the module, where the outer, exposed surface of the edge connectors frictionally contact against an outer surface of corresponding pads arranged within a receptor. The receptor thereby receives the memory module dimensioned according to standards adopted by compact flash card, smart media card, flash path card, multimedia card and secure digital card manufacturers, including the standardized dimensions offered by JEIDA and PCMCIA, for example.
2. Description of the Related Art
The following descriptions and examples are not admitted to be prior art by virtue of their inclusion within this section.
An electronic system is typically known as any device that can receive, transmit, and process electronic signals. Examples of popular electronic systems include the personal computer, personal digital assistant (PDA), digital camera, or any other electronic-based appliance used in a consumer setting. A commonality among all electronic systems is that they employ an interconnection of one or more circuits. Depending on the amount of integration, the circuits can be formed on a single monolithic substrate, often a silicon substrate, henceforth referred to as an integrated circuit.
Typical electronic systems use one or more integrated circuits connected to each other by conductors. Thus, circuits within one integrated circuit can communicate with circuits within another integrated circuit. In order to protect the functionality of the circuits, each integrated circuit is often placed in a package which seals the integrated circuit from the environment. In addition to it being used to protect an integrated circuit, a package can also help distribute signals sent to and from the integrated circuit and, depending on the materials used, the package may also help dissipate heat that occurs during operation of the integrated circuit.
There are numerous types of integrated circuit packages, basically categorized as either ceramic packages or plastic packages. Ceramic packages surround the encased integrated circuit with air, while plastic packages generally employ a resin that fills the space between the integrated circuit and the surrounding package. Plastic packages are often less expensive than ceramic packages. Regardless of whether ceramic or plastic is used, there are numerous package configurations and lead arrangements extending from the package. The leads serve to communicate signals to and from the integrated circuit and, thus, are electrically connected to corresponding bonding pads on the integrated circuit in one of possibly three ways: wire bonds, Tape-Automated Bonding (TAB), or flip-chip. Each of these arrangements are relatively well-known and are used in differing applications based on cost constraints and the density of the integrated circuit bonding pads.
Once the integrated circuit is bonded to the leads and a package is formed about the integrated circuit, the matter of connecting one packaged integrated circuit to another packaged integrated circuit generally involves a printed circuit board or “card.” A card is a rigid, substantially planar backbone element that employs one or more layers of trace conductors separated by a dielectric. The trace conductors extend along one ore more of the conductive layers and, through vias, connect leads of one integrated circuit to leads of another integrated circuit. The printed circuit board can have plated-through holes to accommodate downward extending leads of a packaged integrated circuit, or can simply have a square or rectangular pad on which planar surfaces of the packaged integrated circuit leads can be surface-mounted. The card serves not only to interconnect signals between integrated circuits, but also provides mechanical support for multiple integrated circuits arranged within a chassis of the electronic system. The card thereby suffices to arrange the bonded integrated circuits a spaced distance from each other within the confines of the chassis.
There are numerous ways in which to configure a card and the integrated circuits bonded to that card. For example, FIGS. 1 and 2 illustrate a memory card 10 with edge connectors 12. Edge connectors 12 can be arranged on the backside surface of card 10 near a forward-leading edge 14 of card 10. According to this example, edge 14 can be inserted through a slot 16 extending through a chassis 18 of an electronic system 20.
Memory card 10 can, therefore, be inserted into a receptor 22 that is electrically connected to, for example, another card 24. Like card 10, card 24 may also contain printed conductors and one or more integrated circuits 26 interconnected with each other on a surface of card 24. However, distinguishable from card 24, card 10 is used for a specific purpose that can be universally applied to an electronic system, and is obtainable from numerous vendors in the memory technology sector. Card 10 is therefore a memory card, and utilizes edge connectors 12 that can be frictionally engaged with conductive elements 28 arranged within receptor 22. Connectors 12 are designed to be releasibly inserted into receptor 22.
Shown in FIG. 2 is card 10 illustrated in partial breakaway. Card 10 is shown having one or more integrated circuits 30 connected to each other and to edge conductors 12 by trace conductors 32. A memory card preferably uses some form of memory array. A popular memory array involves an array of non-volatile storage elements. The non-volatile storage elements are preferably configured on a single monolithic silicon substrate, to form a non-volatile memory integrated circuit 30b. Along with circuit 30b is a memory controller 30a. In addition to integrated circuits 30, card 10 may also have mounted thereon discrete devices, such as decoupling or de-bounce capacitors 34. Capacitors 34 serve to minimize transient noise imputed onto trace conductors 32.
In addition to the printed circuit board (or card) on which memory 30b, memory controller 30a, and capacitors 34 are secured, card 10 can also take on a covering 36 which surrounds and protects the integrated circuits and capacitors mounted to card 10. Formed as part of covering 36 is a tab or switch 38 that, when moved, prevents a write operation to the memory integrated circuit. Switch 38 thereby suffices to “write protect” memory card 10. Any signals sent to edge conductors 12 intended to be written onto the storage elements of memory 30b will be prevented from being stored therein if switch 38 is activated. Activation can occur simply by moving switch 38 from one position to another along the sidewall surface of card 10.
The memory card 10 shown in the configuration of FIGS. 1 and 2 gained popularity, for example, during the advent of flash memory. Flash memory can be easily erased and reprogrammed. Once reprogrammed, the data within the flash memory is said to be non-volatile and remains until erased or again reprogrammed. Thus, card 10 can be erased and reprogrammed while in receptor 22 provided, of course, that switch 38 is not in the write protect position. Once programmed, any data stored within non-volatile memory 30b of card 10 will remain, thereby allowing card 10 to be removed and reinserted at a later time whenever that data is needed—similar to a floppy disk.
At present there are numerous types of memory cards having the aforesaid characteristics. Popular such memory cards include: Sony's memory stick, compact flash, smart media, PC cards, flash path, multimedia cards and secure digital. All of the well-known memory cards typically have both a memory controller and non-volatile memory mounted on the card itself, or have the controller form a part of the memory interface, all of which are interconnected to the edge connectors. In order to be usable in multiple electronic systems made by different manufacturers, the industry has imposed a standard on the size of many memory cards. For example, Personal Computer Memory Card International Association (PCMCIA) or Japanese Electronic Industry Development Association (JEIDA) implemented a standard dimension for what are dubbed as Type I, Type II or Type III cards. A Type I memory card measures approximately 2.126×3.37 inches, and is approximately 3.3 mm thick. A Type II memory card is approximately 5.0 mm thick, yet has the same length and width measurements as the Type I card. Under development is a further standard, known as Type III memory card, which is slated to be approximately 10.5 mm thick. All such types of cards are approximately 3.3 mm thick along their guide rails so thinner cards can fit newer, thicker slots. The Type I, Type II, and Type III memory cards are oftentimes referred to as PC cards since the memory cards are sometimes used as a slide-in memory for a personal computer. In addition, multimedia memory cards and secure digital memory cards are often dimensioned 32 mm×24 mm, with a thickness of 1.4 mm or 2.1 mm, respectively. A smart media card is, however, made approximately 45 mm×37 mm, with a thickness of about 0.70-0.88 mm.
Regardless of whether the memory card is dimensioned according to PCMCIA or JEIDA standards, or is dimensioned as a multimedia card, a secure digital card, a compact flash card, a smart media card or a flash path card, the memory card is one that must fit in a receptor specifically designed to receive a memory card manufactured by one of numerous manufacturers. Additionally, the memory card is considerably larger than a conventional packaged integrated circuit, which generally has no defined outer dimension since a packaged integrated circuit does not bear edge connectors placed only at one edge of the integrated circuit package for slide engagement into a receptor of an electronic system. Such systems include digital cameras, laptap computers, handheld PDAs that often have a slot to receive additional memory afforded by the memory card. The secure digital memory card can have a mechanical switch mounted on the outer covering to prevent writing of data to the integrated circuit. Various other memory cards may or may not have such a switch.
It would be desirable to be able to manufacture a memory card using a conventional edge connector arrangement employed by memory cards, and dimensioned according to standards used by legacy memory card manufacturers. The desired memory card would, however, avoid using a printed circuit board or card for electrical routing or as a backbone for mechanical stability. The desired memory card could be classified as a memory module made of less expensive materials and in less time than conventional memory cards. The desired memory module avoids the most expensive component of a memory card by eliminating the cost and lead time needed to form package material about an integrated circuit, form printed conductors upon and within a card, and form the connection between leads of the integrated circuit and printed conductors upon (or within) the card.